Generators, like those used in the power-generation industry, basically comprise a rotor and a stator. The rotor is attached to a prime mover, such as a steam turbine or gas turbine, which provides mechanical energy to spin the rotor inside of the stator. When the rotor is also provided with an excitation current, electricity is induced in the stator of the generator.
FIG. 1 illustrates cooling in one type of generator rotor. The rotor includes a plurality of slots formed in the body of the rotor. The slots are filled with conductors called rotor coils. At the ends of the rotor, the rotor coils make turns and re-enter the rotor. These turns are called end turns. To prevent the portions of the rotor coils near the ends of the rotor from flying out under centrifugal force, the end turn areas are contained by a retaining ring and end plate assembly.
When the rotor 2 is spinning, cooling gas 4 such as air or hydrogen is drawn into the gap between the rotor shaft and the end plate 6. In the rotor of FIG. 1, the cooling gas passes through the end turns 8 and then exits through exhaust holes in the rotor 10. Also present on the end plate 6 are balance holes 12, which in different types of generators may be a continuous groove in which weights are placed. A number of other cooling arrangements exist. Methods and systems consistent with the present invention are suitable for use with multiple cooling arrangements, as will be understood by one of skill in the art.
In order to improve the flow characteristics of the cooling gas through a rotor, guidevanes may be installed in the generator. Guidevanes help guide the cooling gas that is entering the rotor so that it flows more linearly and is distributed more evenly around the rotor. U.S. Pat. No. 4,547,688, which is incorporated by reference herein in its entirety, illustrates a conventional guidevane that is included as part of a rotor when a generator is manufactured.
FIG. 2 illustrates a guidevane of the prior art. A guidevane 20 is essentially an arc that fits on the inner diameter of the end plate. Typically there are four guidevanes installed around the end plate, however this may be varied. The guidevanes have turning vanes 22 that come within fractions of an inch from the rotor shaft and direct the airflow more efficiently into the rotor. Without guidevanes the airflow into the generator is less efficient and therefore entire efficiency of the generator is reduced.
To attach the guidevanes to the generator, the guidevanes are bolted to the inner circumference of the end plate by means of bolt holes 24 located on the flat surface of the guidevanes. Unfortunately, this arrangement requires complete access to the end plate when the rotor is not yet installed. Also, even when fully accessible, the attachment of the guidevanes can be difficult and time consuming. What is needed is a method and apparatus that can install guidevanes in a more efficient manner, and further can be used with fully assembled generators.
Other difficulties with the prior art also exist, some of which will be apparent upon further reading.